I say the large capacity magazines are part of the problem and perhaps banning them is the most important part of the new AWB. I say that based on the Loughner case in which it seemed clear that he killed more people than he would have due to the 30-round magazine he used. I say it based on the Aurora shooting, in which Holmes used a 100-round drum and probably did more damage as a result. And I base it on the Lanza shooting where it seems entirely possible that if he'd had to change magazines more often, fewer kids might have died.
La Pierre and his sycophants keep telling us it would do no good, but that same rationale does not apply to murder. We don't argue for de-criminalizing murder because we still have them in spite of the law. No, we try to find ways to prevent them, first by making it illegal.